Netty是如何綁定端口和啟動(dòng)服務(wù)的

public final class NettyServer {public static void main(String[] args) throws Exception {        EventLoopGroup bossGroup = new NioEventLoopGroup();        EventLoopGroup workerGroup = new NioEventLoopGroup();try {            ServerBootstrap serverBootstrap = new ServerBootstrap();            serverBootstrap.group(bossGroup, workerGroup)                    .channel(NioServerSocketChannel.class)                    .childHandler(new ChannelInitializer<SocketChannel>() {@Overridepublic void initChannel(SocketChannel channel) {                            ChannelPipeline channelPipeline = channel.pipeline();                            channelPipeline.addLast("decoder", new StringDecoder());                            channelPipeline.addLast("encoder", new StringEncoder());                            channelPipeline.addLast("handler", new ServerHandler());                        }                    });            ChannelFuture channelFuture = serverBootstrap.bind(8888).sync();            channelFuture.channel().closeFuture().sync();        } finally {            bossGroup.shutdownGracefully();            workerGroup.shutdownGracefully();        }    }}br

public class ServerHandler extends ChannelInboundHandlerAdapter {    @Override    public void channelActive(ChannelHandlerContext ctx) {        System.out.println("channelActive");    }    @Override    public void channelRegistered(ChannelHandlerContext ctx) {        System.out.println("channelRegistered");    }    @Override    public void handlerAdded(ChannelHandlerContext ctx) {        System.out.println("handlerAdded");    }    @Override    public void channelReadComplete(ChannelHandlerContext ctx) throws Exception {        System.out.println("channelReadComplete");    }    @Override    public void channelInactive(ChannelHandlerContext ctx) throws Exception {        System.out.println("channelInactive");    }    @Override    public void channelRead(final ChannelHandlerContext ctx, Object msg) throws Exception {        System.out.println("service receive msg:" + msg);    }}br

reStructuredTexthandlerAddedchannelRegisteredchannelActivebr

reStructuredTextservice receive msg:xxxchannelReadCompletebr

public ChannelFuture bind(int inetPort) {return bind(new InetSocketAddress(inetPort));}//通過(guò)端口號(hào)創(chuàng)建一個(gè)`InetSocketAddress`，然后繼續(xù)調(diào)用重載的`bind()`public ChannelFuture bind(SocketAddress localAddress) {// ...return doBind(localAddress);}br

private ChannelFuture doBind(final SocketAddress localAddress) {//...final ChannelFuture regFuture = initAndRegister();//...final Channel channel = regFuture.channel();//...    doBind0(regFuture, channel, localAddress, promise);//...return promise;br

final ChannelFuture initAndRegister() {    Channel channel = null;// 新建Channel    channel = channelFactory.newChannel();// 初始化Channelinit(channel);// 將這個(gè)Channel Register到某個(gè)對(duì)象    ChannelFuture regFuture = config().group().register(channel);return regFuture;}br

public B channel(Class<? extends C> channelClass) {if (channelClass == null) {throw new NullPointerException("channelClass");    }return channelFactory(new ReflectiveChannelFactory<C>(channelClass));}br

public class ReflectiveChannelFactory<T extends Channel> implements ChannelFactory<T> {private final Class<? extends T> clazz;public ReflectiveChannelFactory(Class<? extends T> clazz) {if (clazz == null) {throw new NullPointerException("clazz");        }this.clazz = clazz;    }@Overridepublic T newChannel() {try {return clazz.newInstance();        } catch (Throwable t) {throw new ChannelException("Unable to create Channel from class " + clazz, t);        }    }}br

public NioServerSocketChannel() {this(newSocket(DEFAULT_SELECTOR_PROVIDER));}private static ServerSocketChannel newSocket(SelectorProvider provider) {try {// 利用SelectorProvider產(chǎn)生一個(gè)ServerSocketChannel對(duì)象return provider.openServerSocketChannel();    } catch (IOException e) {throw new ChannelException("Failed to open a server socket.", e);    }}br

public NioServerSocketChannel(ServerSocketChannel channel) {super(null, channel, SelectionKey.OP_ACCEPT);    config = new NioServerSocketChannelConfig(this, javaChannel().socket());}br

protected AbstractNioMessageChannel(Channel parent, SelectableChannel ch, int readInterestOp) {super(parent, ch, readInterestOp);}protected AbstractNioChannel(Channel parent, SelectableChannel ch, int readInterestOp) {super(parent);this.ch = ch;// 設(shè)置SelectionKey.OP_ACCEPT事件this.readInterestOp = readInterestOp;// 設(shè)置ServerSocketChannel為非阻塞的    ch.configureBlocking(false);}br

protected AbstractChannel(Channel parent) {this.parent = parent;    id = newId();unsafe = newUnsafe();    pipeline = newChannelPipeline();}br

void init(Channel channel) throws Exception {// 給channel設(shè)置optionfinal Map<ChannelOption<?>, Object> options = options0();synchronized (options) {        channel.config().setOptions(options);    }// 給channel設(shè)置attrfinal Map<AttributeKey<?>, Object> attrs = attrs0();synchronized (attrs) {for (Entry<AttributeKey<?>, Object> e: attrs.entrySet()) {            AttributeKey<Object> key = (AttributeKey<Object>) e.getKey();            channel.attr(key).set(e.getValue());        }    }    ChannelPipeline p = channel.pipeline();final EventLoopGroup currentChildGroup = childGroup;final ChannelHandler currentChildHandler = childHandler;final Entry<ChannelOption<?>, Object>[] currentChildOptions;final Entry<AttributeKey<?>, Object>[] currentChildAttrs;synchronized (childOptions) {// 設(shè)置新接入channel的options        currentChildOptions = childOptions.entrySet().toArray(newOptionArray(childOptions.size()));    }synchronized (childAttrs) {// 設(shè)置新接入channel的attrs        currentChildAttrs = childAttrs.entrySet().toArray(newAttrArray(childAttrs.size()));    }    p.addLast(new ChannelInitializer<Channel>() {@Overridepublic void initChannel(Channel ch) throws Exception {final ChannelPipeline pipeline = ch.pipeline();// 設(shè)置handler到pipeline上// 這里的handler()返回的就是.handler()所設(shè)置的值            ChannelHandler handler = config.handler();if (handler != null) {                pipeline.addLast(handler);            }            ch.eventLoop().execute(new Runnable() {@Overridepublic void run() {// p.addLast()向serverChannel的流水線(xiàn)處理器中加入了一個(gè)ServerBootstrapAcceptor// 從名字上就可以看出來(lái)這是一個(gè)接入器，專(zhuān)門(mén)接受新請(qǐng)求，把新的請(qǐng)求扔給某個(gè)事件循環(huán)器                    pipeline.addLast(new ServerBootstrapAcceptor(currentChildGroup, currentChildHandler, currentChildOptions, currentChildAttrs));                }            });        }    });}br

ChannelFuture regFuture = config().group().register(channel);```此處`config().group()`返回的對(duì)象為`NioEventLoopGroup````java@Overridepublic ChannelFuture register(Channel channel) {// 調(diào)用了NioEventLoop對(duì)象中的register方法// NioEventLoop extends SingleThreadEventLoopreturn next().register(channel);}br

public ChannelFuture register(Channel channel) {    return register(new DefaultChannelPromise(channel, this));}public ChannelFuture register(final ChannelPromise promise) {    ObjectUtil.checkNotNull(promise, "promise");    promise.channel().unsafe().register(this, promise);    return promise;}br

public final void register(EventLoop eventLoop, final ChannelPromise promise) {// ...    AbstractChannel.this.eventLoop = eventLoop;// ...    register0(promise);}br

private void register0(ChannelPromise promise) {    try {        boolean firstRegistration = neverRegistered;        doRegister();        neverRegistered = false;        registered = true;        pipeline.invokeHandlerAddedIfNeeded();        safeSetSuccess(promise);        pipeline.fireChannelRegistered();        if (isActive()) {            if (firstRegistration) {                pipeline.fireChannelActive();            } else if (config().isAutoRead()) {                beginRead();            }        }    } catch (Throwable t) {        closeForcibly();        closeFuture.setClosed();        safeSetFailure(promise, t);    }}//這一段其實(shí)也很清晰，先調(diào)用`doRegister()`進(jìn)行注冊(cè)protected void doRegister() throws Exception {    boolean selected = false;    for (;;) {        try {            selectionKey = javaChannel().register(eventLoop().unwrappedSelector(), 0, this);            return;        } catch (CancelledKeyException e) {            // ...        }    }}br

private static void doBind0(final ChannelFuture regFuture, final Channel channel, final SocketAddress localAddress, final ChannelPromise promise) {    channel.eventLoop().execute(new Runnable() {@Overridepublic void run() {if (regFuture.isSuccess()) {                channel.bind(localAddress, promise).addListener(ChannelFutureListener.CLOSE_ON_FAILURE);            } else {                promise.setFailure(regFuture.cause());            }        }    });}//在`dobind0()`方法中通過(guò)`EventLoop`執(zhí)行一個(gè)任務(wù)，接下來(lái)我們進(jìn)入到`channel.bind()`方法public ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {return pipeline.bind(localAddress, promise);}public final ChannelFuture bind(SocketAddress localAddress, ChannelPromise promise) {return tail.bind(localAddress, promise);}br

public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {unsafe.bind(localAddress, promise);}//這里的`unsafe`就是前面提到的`AbstractUnsafe`, 準(zhǔn)確點(diǎn)應(yīng)該是`NioMessageUnsafe`@Overridepublic final void bind(final SocketAddress localAddress, final ChannelPromise promise) {// ...    boolean wasActive = isActive();// ...    doBind(localAddress);if (!wasActive && isActive()) {        invokeLater(new Runnable() {            @Overridepublic void run() {                pipeline.fireChannelActive();            }        });    }    safeSetSuccess(promise);}//在`doBind`方法中完成綁定操作，代碼如下protected void doBind(SocketAddress localAddress) throws Exception {if (PlatformDependent.javaVersion() >= 7) {        javaChannel().bind(localAddress, config.getBacklog());    } else {        javaChannel().socket().bind(localAddress, config.getBacklog());    }}br

public void channelActive(ChannelHandlerContext ctx) throws Exception {    ctx.fireChannelActive();    readIfIsAutoRead();}//`pipeline.channelActive`會(huì)逐一調(diào)用`pipeline`中每一個(gè)節(jié)點(diǎn)的`channelActive`方法，所以`HeadContext`的`channelActive`將會(huì)被調(diào)用，即`readIfIsAutoRead`方法將會(huì)被調(diào)用public void channelActive(ChannelHandlerContext ctx) throws Exception {    ctx.fireChannelActive();    readIfIsAutoRead();}private void readIfIsAutoRead() {if (channel.config().isAutoRead()) {        channel.read();    }}//最終這個(gè)方法會(huì)調(diào)用到`AbstractNioChannel`的`doBeginRead`方法protected void doBeginRead() throws Exception {final SelectionKey selectionKey = this.selectionKey;if (!selectionKey.isValid()) {return;    }    readPending = true;final int interestOps = selectionKey.interestOps();if ((interestOps & readInterestOp) == 0) {        selectionKey.interestOps(interestOps | readInterestOp);    }}br

ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();// 建NioServerSocketChannelserverSocketChannel.configureBlocking(false);//AbstractNioChannel中ch.configureBlocking(false);serverSocketChannel.bind(new InetSocketAddress("localhost", 8888));// NioServerSocketChannel.doBind()Selector selector = Selector.open();// NioEventLoop.openSelector()serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT) //  AbstractNioChannel.doBeginRead()br